Re: [RFC 2/4] firewire: dynamic cdev allocation below firewire major

[Stefan Richter <stefanr@s5r6.in-berlin.de>]

Johannes Berg wrote:
> This  patch implements dynamic minor number allocation below the 171
> major allocated for ieee1394. Since on today's systems one doesn't need
> to have fixed device numbers any more we could just use any, but it's
> probably still useful to use the ieee1394 major number for any firewire
> related devices (like mem1394).
[...]
> --- a/drivers/ieee1394/ieee1394_core.h
> +++ b/drivers/ieee1394/ieee1394_core.h
> @@ -186,19 +186,38 @@ void hpsb_packet_received(struct hpsb_ho
>   * 171:0-255, the various drivers must then cdev_add() their cdev
>   * objects to handle their respective sub-regions.
>   *
> + * Alternatively, drivers may use a dynamic minor number character
> + * device by using the functions hpsb_cdev_add and hpsb_cdev_del.
> + * hpsb_cdev_add requires an initialised struct cdev and will add
> + * it with cdev_add() automatically, reserving a new minor number
> + * for the new device (unless cdev_add() fails). It returns the
> + * status of cdev_add(), or -ENODEV if no minor could be allocated.

This comment should be moved to the implementations of respective 
functions and be formatted as described by 
Documentation/kernel-doc-nano-HOWTO.txt. (We should eventually check all 
exported ieee1394 symbols if they are documented that way.)

> + * Currently 64 minor numbers are reserved for that, if necessary
> + * this number can be increased by simply adjusting the constant
> + * IEEE1394_MINOR_DYNAMIC_FIRST.
> + *
>   * Minor device number block allocations:
>   *
>   * Block 0  (  0- 15)  raw1394
>   * Block 1  ( 16- 31)  video1394
>   * Block 2  ( 32- 47)  dv1394
>   *
> - * Blocks 3-14 free for future allocation
> + * Blocks 3-10 free for future allocation
>   *
> + * Block 11 (176-191)  dynamic allocation region
> + * Block 12 (192-207)  dynamic allocation region
> + * Block 13 (208-223)  dynamic allocation region
> + * Block 14 (224-239)  dynamic allocation region
>   * Block 15 (240-255)  reserved for drivers under development, etc.
>   */
>  
>  #define IEEE1394_MAJOR			 171
>  
> +#define IEEE1394_MINOR_DYNAMIC_FIRST	176
> +#define IEEE1394_MINOR_DYNAMIC_LAST	239
> +#define IEEE1394_MINOR_DYNAMIC_COUNT	(IEEE1394_MINOR_DYNAMIC_LAST-IEEE1394_MINOR_DYNAMIC_FIRST+1)
> +
>  #define IEEE1394_MINOR_BLOCK_RAW1394	   0
>  #define IEEE1394_MINOR_BLOCK_VIDEO1394	   1
>  #define IEEE1394_MINOR_BLOCK_DV1394	   2
> @@ -218,6 +237,11 @@ static inline unsigned char ieee1394_fil
>  	return file->f_dentry->d_inode->i_cindex;
>  }
>  
> +/* add a dynamic ieee1394 device */
> +int hpsb_cdev_add(struct cdev *chardev);
> +/* remove a dynamic ieee1394 device */
> +void hpsb_cdev_del(struct cdev *chardev);
[...]

Again, better no comment here than these two which are not very 
enlightening.
-- 
Stefan Richter
-=====-=-==- --=- --=-=
http://arcgraph.de/sr/